Objectives The purpose of this study is to confirm the mediation effects of Perceived social support and Self-compassion when Unstable attachment of the early stages of adulthood affects Interpersonal competence. Methods A self-report online survey was conducted on 497 people in early adulthood aged 19-39 nationwide, the total of 436 data were used for analysis, except for missing responses or unfaithful responses among the data. As a scale, Unstable attachment, Avoidance attachment, Perceived social support, Self-compassion, and Interpersonal Competence were used, and the collected data were analyzed by SPSS 21.0 and PROCESS Macro 3.5. Results First, Unstable attachment and Avoidance attachment were negatively correlated with Perceived social support, Self-compassion and Interpersonal Competence, Perceived social support, Self-compassion and Interpersonal Competence showed a positive correlation. Second, Unstable attachment did not have a direct effect on Interpersonal Competence, but had a complete mediating effect that had a indirect effect through Perceived social support and Self-compassion as a mediation. Avoidance attachment had a direct effect on Interpersonal Competence, and had a partial mediating effect that indirectly affects Perceived social support and Self-compassion as a mediation. Third, Unstable attachment and Avoidance attachment showed to affect Interpersonal Competence by sequentially double-mediating Perceived social support and Self-compassion. Conclusions This study is expected to help to intervene the counseling for counselee who have a difficulty in the interpersonal relationship by confirming that Perceived social support and Self-compassion were sequentially dual mediated in the process of Unstable attachment and Avoidance attachment affecting Interpersonal competence.